International environmental law has evolved rapidly in recent decades and is now a highly sophisticated and distinctive sub-discipline of public international law that regulates a broad array of human activities affecting natural and built environments. Yet despite the marked increase in the scope and content of this legal field the scale and pace of environmental destruction has also grown. It is estimated that over 60 per cent of all ecosystem services that support life on earth have been degraded or are being used unsustainably, including freshwater resources and natural systems for air and water purification. This is leading to continuing loss of biodiversity and is also preventing effective action against poverty, hunger, and health crises in many parts of the globe.

With the notable exception of climate change, where there is an urgent need to develop and implement an effective regime that builds upon the achievements to date, the main challenge for international environmental law in the twenty-first century is implementing an impressive body of law already in existence. This is a challenge of environmental governance, requiring the design and operation of institutions that can promote the full and faithful observance by states of their environmental commitments. International adjudication, comprising both arbitration and judicial settlement by international courts and tribunals, is one type of institution gaining increasing prominence in this context. Factors behind this include increasing awareness of international disputation over shared natural resources, and the growth of environmental and other relevant treaties containing dispute settlement mechanisms.